The present invention relates to apparatus and methods for medical radiographic examination. More particularly, the invention is directed to improved apparatus and techniques for carrying out diagnostic X-ray examinations and for detecting internal growths including tumors, cancer and other types of defects and abnormalities. Specifically, the invention describes an improved body-supporting apparatus for the selective and controlled orientational positioning of a subject so as to provide improved fidelity and enhanced diagnostic value for the radiographic film images produced, particularly in mammography.
The subject invention augments and is an improvement over the technique and apparatus described in Harold J. Lasky U.S. Pat. No. 3,578,971 for Mammographic X-ray Apparatus and Technique, and the entire disclosure of that patent is hereby specifically incorporated herein by reference to the extent it is not inconsistant herewith.
Radiographic examination procedures have been widely used in the past for medical diagnosis and to detect tumorous body growths. In the specific application known as mammography, the techniques have been applied to the detection of breast tumors, cancer, and other growths, in the adult female breast. In widely employed prior art diagnostic procedures it has been necessary to expose the subject to relatively large quantities of radiation. Additionally, for the most part, prior art techniques have failed to distinguish non-palpable growths in spite of the use of such excessively high radiation levels.
Lasky U.S. Pat. No. 3,578,971 referred to above describes an improved method for X-ray examination of the breast of a female subject under conditions which permit minimal radiation exposure and ensure optimum fields of examination, sharp image focus, and even image density. A substantive feature of the technique is the carrying out of the radiographic examination while gently yet firmly compressing the breast of a female subject, while the breast is gravitationally suspended. In using the apparatus described in the above-referred to patent it is necessary for the patient to stand at the foot of a table, facing the X-ray tube, and bend forward or lean over so as to suspend the breast between tissue embracing walls of the device. Compression force is then applied to the tissue. A standing position is used for both the cephalocaudal view and the lateral-medial views.
While the technique and the apparatus of the above described patent have proven useful and diagnostically valuable, certain shortcomings have now been noted. For example, the angle at which the gravitationally suspended breast of the standing subject depends affects the orientation of the tissue relative to the radiation source used. Only minimal variation or adjustment is feasible, a limitation which has been found significant. The present invention stems from and invokes the concept that the precise physical orientation of the suspended tissue is critical in achieving optimum image fidelity coupled with minimal radiation exposure.
It is a feature of the present invention that the manipulable cradle or body support makes possible positioned gravitational suspension of the breast tissue in each of a series of diverse selectible angles to facilitate definitive, precisely controlled exposure of the tissue in diagnostic radiological procedures.
Another feature of the invention is that it includes a table or cradle which comfortably supports the patient in any medically preferred disposition or spacial orientation so as to minimize patient movement and to obviate patient fatigue.
A related advantage of the invention is that it allows radiation exposures to be taken at varied, yet controlled and reproducible relative angles to provide a more meaningful series of film displays, thereby to enhance the reliability and usefulness of diagnoses.
Yet another advantage of the invention is that a complete series of exposures may be made at extremely low radiation intensities and dosages so as to minimize any potentially hazardous radiation effects.
Yet another important feature of the invention is that it includes means whereby the subject-supporting table may be simply and rapidly manipulated about each of a pair of mutually perpendicular horizontal axes so that any required angle of tissue suspension, relative to the body of the subject, may be easily achieved.
A related feature of the invention is that is includes apparatus whereby tissue contacting and compressing walls may be elevated, shifted, and rotated independently of the body support table itself, thus ensuring complete versatility and ready adaptation in all modes of patient support.
A related feature of the invention is that, by recording the various manipulation, settings and adjustment parameters, the examining physician is able to reproduce precisely a viewing field corresponding to one previously used, so that exact and meaningful comparisons of tissue condition may be made as a function of time.
The present invention makes it possible to examine the breast of a female subject under conditions such that the internal structures are radiographically displayed for diagnostic visualization, in their most orderly anatomic arrangement and under conditions of reduced and substantially uniform tissue thickness to permit minimal radiation exposure and to ensure optimum field of examination, sharp image focus, and more even image density.
It is a feature of the apparatus and method of the invention that it is possible to reduce the intensity of radiation as well to decrease the scattering of radiation energy. It is a general feature of the invention in that it provides an improved technique and apparatus for the diagnostic X-ray examination of the female breast under conditions of complete immobilization of breast tissue, yet without any discomfort to or fatigue of the subject.
A feature of the invention is that the subject-supporting table may be tilted about a horizontal axis in a manner so as to effect minimal lateral disorientational displacement of the patent's subtended breast.
A related feature of the invention is that the subject-supporting table may be pivoted about each of a pair of parallel, laterally-spacial longitudinally-extending axes so as to minimize lateral shifting of the breast as its dependence angle relative to the subject's body is varied.
It is an important feature of the invention that the cooperating elements of the weight-bearing frame are positioned very close to one another so as to establish a pivotal or fulcrum point as close as possible to the estimated center of each breast whereby when the cradle is titled transversely at that fulcrum, movement of the breast relative to the compression device is minimized, requiring minimal adjustment of the X-ray tube and conpression device in changing from one breast to the other.